1. Field of the Invention
The invention relates to an optical module. More particularly, the invention relates to a light source module and a wavelength conversion module.
2. Description of Related Art
With development of display technology, a projection apparatus may use an ultra high pressure lamp (UHP lamp) for emitting white light together with a color wheel to sequentially generate red light, green light, and blue light, so that the projection apparatus can provide color images. In recent years, a projection apparatus using red, green, and blue light emitting diodes (LEDs) as light sources is further developed.
In the projection apparatus using the LEDs as the light sources, beams emitted from the red, green, and blue LEDs are combined through a light combination system, so that different color beams from different propagating directions can be guided to a same direction. Since a brightness of such projection apparatus is determined by brightness of the LEDs in such kind of projection apparatus, and the green LED is the light source of main brightness contribution, the whole brightness of the projection apparatus depends on a light emitting efficiency of the green LED. However, the light emitting efficiency of the existing green LED is low, and is not suitable to serve as the light source of a high brightness projector.
U.S. Pat. No. 6,762,785 discloses a light source module including a red light source, a green light source, a blue-green light source, and a blue light source. FIG. 1 of U.S. Pat. No. 7,445,340 discloses an LED for generating a blue beam or an ultraviolet beam, and the light beam is reflected by an optical polarization beam splitter and propagated to a reflector, and then the light beam is absorbed by phosphor powder to excite a green beam. FIG. 3a and FIG. 4 of U.S. Pat. No. 7,547,114 disclose a wheel having light conversion materials such as phosphors, and the beam emitted from the LED irradiates the wheel, so that light beams of a plurality of colors can be generated through the excitation of the light conversion materials. FIG. 1 of U.S. Pat. No. 7,070,300 discloses an LED light source, an enhanced light emitting structure, and phosphor powder. According to FIG. 4 of U.S. Patent Publication No. 20090262308, a blue exciting beam generated by a light source is propagated to the phosphor powder coated on a light transparent device, so as to generate a green beam. This green beam is combined with another green beam from a green light source to generate a combined green beam. A dichroic mirror is used to combine a red beam, the combined green beam, and a blue beam into an illumination beam. FIG. 4 and FIG. 5 of Japan Patent No. 2009-150938 disclose that an exciting beam generated by a blue exciting light source is reflected within an optical cavity, and is guided to a phosphor material to generate the green beam.